We have continued our study of the possible age-dependent relaxation of specific gene expression in tissues where the presence of these genes is not expected. These studies have now included the structural genes: alpha and Beta globin, casein and alpha-fetoprotein, and the endogenous C-type viruses: mouse leukemia virus (MuLV) and mouse mammary tumor virus (MMTV). Both globin an alpha-fetoprotein RNA appear to increase in nuclei and cytoplasm of the liver for the long-lived C57BL/6J mouse strain and globin RNA in the nuclei and cytoplasm of the brain for this strain. Of particular interest is the high fraction of globin RNA found only in the liver nuclei of the old AKR mouse strain. This mouse strain has a high incidence of leukemia. A high age-dependent increase in MuLV-RNA in thymus but not in liver and brain was also found for the AKR strain. Although MuLV-RNA was found to increase with age in the nuclei and cytoplasm of liver and brain in the long-lived C57BL/6J mouse stain, MMTV-RNA was found to increase only in liver nuclei. Globin RNA also appears to increase with age in human brain, as was previously found to occur in brain tissues of the mouse.